PECVD methods for producing ultra low-k dielectric films using UV treatment

Abstract

Methods of preparing low-k carbon-doped oxide (CDO) films having high mechanical strength are provided. The methods involve contacting the substrate with a CDO precursor to deposit the film typically using a plasma-enhanced chemical vapor deposition (PECVD) method. After the film is deposited, it is exposed to ultraviolet radiation in a manner that increases cross-linking and/or lowers the dielectric constant of the film. The resulting films have ultra-low dielectric constants, e.g., about 2.5, but also high mechanical strength, e.g., a modulus of at least about 7.5 GPa. In certain embodiments, a single hydrocarbon precursor is used, resulting in an improved process for obtaining ULK films that does not require dual (porogen and backbone) precursors.

1. A method of preparing a low-k doped silicon oxide (CDO) film on a substrate, the method comprising:
 providing the substrate to a deposition chamber; 
 contacting the substrate with a process gas comprising a silicon-containing precursor having a carbon-carbon triple bond and a carrier gas to thereby deposit a solid CDO film containing carbon-carbon triple bonds on the substrate via a dual RF frequency PECVD reaction, wherein the process gas contains no more than one hydrocarbon-containing precursor; and 
 exposing the deposited film to UV radiation in a manner that improves cross-linking and lowers the dielectric constant of the film. 
 
     
     
       2. The method of  claim 1  wherein the dielectric constant of the film is between about 2.5 and 2.7. 
     
     
       3. The method of  claim 1  wherein the dielectric constant of the film is less than or equal to about 2.5. 
     
     
       4. The method of  claim 1  wherein after exposing the deposited film to UV radiation, the deposition film has a pore diameter distribution having a peak between about 1.15-1.30 nm. 
     
     
       5. The method of  claim 1  wherein the process gas consists essentially of an organo-silicon precursor, an optional oxidant and a carrier gas. 
     
     
       6. The method of  claim 5  wherein the process gas contains an oxidant selected from: molecular oxygen (O 2 ), ozone (O 3 ), hydrogen peroxide (H 2 O 2 ), nitrous oxide (N 2 O) and carbon dioxide (CO 2 ). 
     
     
       7. The method of  claim 1  wherein the silicon-containing precursor is selected from: Trimethylsilaneacetylene (TMSA), Bis(trimethylsilyl)acetylene, (BTMSA), Propargyltrimethylsilane (PTMS), Propargyloxytrimethylsilane (POTMS), 1,3-Diethynyltetramethyldisiloxane (DTDS), Dimethylmethoxysilaneacetylene (DMMOSA), Methyldimethoxysilaneacetylene (MDMOSA), Dimethylethoxysilaneacetylene (DMEOSA), Methyldiethoxysilaneacetylene (MDEOSA), Ethyldiethoxysilaneacetylene (EDEOSA), Dimethylsilane-diacetylene DMSDA, Methylsilane-triacetylene (MSTA) and Tetraacetylene Silane (TAS). 
     
     
       8. The method of  claim 1  wherein in the silicon-containing precursor is selected from Trimethylsilaneacetylene (TMSA), Bis(trimethylsilyl)acetylene, (BTMSA). 
     
     
       9. The method of  claim 1  wherein a CH 2 —Si—CH 2 /Si—CH 3  FTIR peak area ratio of the deposited film is at least about 15% after exposing the film to UV radiation. 
     
     
       10. The method of  claim 1  wherein a CH 2 —Si—CH 2 /Si—CH 3  FTIR peak area ratio of the deposited film is at least about 20% after exposing the film to UV radiation. 
     
     
       11. The method of  claim 1  wherein a CH 2 —Si—CH 2 /Si—CH 3  FTIR peak area ratio of the deposited film is at least about 30% after exposing the film to UV radiation. 
     
     
       12. The method of  claim 1  wherein the deposited film has a pore interconnectivity of about zero. 
     
     
       13. The method of  claim 1  wherein there is substantially no out-gassing for the deposited film. 
     
     
       14. The method of  claim 1  wherein the methanol diffusion coefficient is less than about 100 μm 2 /sec. 
     
     
       15. A method of preparing a low-k doped silicon oxide (CDO) film on a substrate, the method comprising:
 providing the substrate to a deposition chamber; 
 contacting the substrate with a process gas comprising a silicon-containing precursor having a carbon-carbon triple bond and a carrier gas to thereby deposit a CDO film containing carbon-carbon triple bonds on the substrate via a dual RF frequency PECVD reaction; and 
 exposing the deposited film to UV radiation to thereby lower the dielectric constant to no more than about 2.7 and increase a Young's modulus of the film. 
 
     
     
       16. The method of  claim 15  wherein the modulus is increased to at least about 12 GPa. 
     
     
       17. The method of  claim 15  wherein the dielectric constant is lowered to no more than about 2.6 and the modulus is increased to at least about 9 GPa. 
     
     
       18. The method of  claim 15  wherein the dielectric constant is lowered to no more than about 2.5 and the modulus is increased to at least about 7 GPa. 
     
     
       19. The method of  claim 15  wherein the process gas contains no more than one hydrocarbon precursor. 
     
     
       20. The method of  claim 15  wherein the process gas does not contain a porogen. 
     
     
       21. The method of  claim 15  wherein the film is deposited at a temperature of about 350-400 C. 
     
     
       22. The method of  claim 15  wherein the precursor is selected from BTMSA and TMSA. 
     
     
       23. The method of  claim 15  wherein exposing the film to UV radiation increases the CH 2 —Si—CH 2 /Si—CH 3  FTIR peak area ratio by at least about 100%.